It's not easy being an NBA head coach these days (although being a millionaire helps). A record 12 of the league's 30 teams have let their coach go this off-season, and six of those clubs actually made the playoffs. But in this age of the punitive luxury tax, when developing the players you draft is even more premium, teams are less patient with their bench gurus.

But do teams have any idea what makes a good coach?

Not really. NBA coaching is something of a catch-22: You need to be successful in order to be successful. Coaches need the credibility to get players who are much less replaceable (and know it) to buy into their system and roles. In other words, it's not as much about Xs and Os -- there are only so many ways to run or defend a pick-and-roll -- as it is about managing egos and motivating players. That's why teams gravitate towards former head coaches, assistant coaches from top clubs, and players -- they can convincingly say they know what it takes to win in the league. (And that's possibly why college coaches who try to transition to the pros tend to have a harder time).

Of course, it's still a crap-shoot. Economists have found that most coaches don't statistically improve their teams' performances in any significant way. But what if front offices hired assistants from the few teams that have head coaches who make a difference? Matthew Yglesias of Slate thinks that might be the next frontier in exploitable inefficiencies: Rather than bringing in retreads or retired players, teams should poach top assistants from the Spurs or Lakers. In particular, Yglesias thinks the New jersey Nets should have opted for former Lakers guard and Phil Jackson assistant Brian Shaw over the very recently retired former Nets star Jason Kidd.

But Matt should pay closer attention to recent history: Hiring a former assistant coach from a successful team is the most wrinkled page in the GM playbook.

Economists have found that most coaches don't statistically improve their teams' performances in any significant way

I went looking for an article to back this up and this was the most interesting one I found after a little googling. I don't know how you isolate the affect of the coach versus team composition, but it's interesting that several studies were done in different sports and all came to roughly the same conclusion: that in a given sport most coaches are so similar they can be easily interchanged.

Maybe there's debate among sport economists about the statistical techniques these studies used or something.

This article was too long for me to read (because there's construction going on outside and I'm a lazy bloodclot), but the table of coaches impact is pretty interesting: basically only Phil Jackson and Greg Popovich are measurably better than the average coach.